I bought a variety of colored beans for around $1 a bag. I poured them into the water table and gave the girls some cups, bowls, spoons, etc. to play with.
Try it out with your little ones. You could also use a big storage tub if you don't have a water table.
We made the rules in the beginning - you cannot dump the beans on the floor on purpose. If you do it on accident then pick them up. Ariel had to learn the hard way. She filled a cup, climbed up on a chair and poured them out. I had already reminded her a few times so she had to sit in time out for a moment.